c++实现矩阵乘法

重载*运算符为友元函数。

  1 #include <iostream>
  2 #include <cmath>
  3 using namespace std;
  4
  5 class Matrix{
  6     public:
  7         Matrix(){}
  8         Matrix(int,int);
  9         void setMatrix();
 10         void showMatrix();
 11         void showTransposedMatrix();
 12         friend Matrix operator *(Matrix m1,Matrix m2);
 13     protected:
 14         int m;
 15         int n;
 16         int mn;
 17         double* matrixPtr;
 18         double* transposedMPtr;
 19         void transpose();
 20 };
 21
 22 class SquareMatrix:public Matrix{
 23     public:
 24         SquareMatrix(){}
 25         SquareMatrix(int);
 26         void setSquareMatrix();
 27         void setDet();
 28         void getDet();
 29     private:
 30         double det;
 31 };
 32
 33 Matrix::Matrix(int mt,int nt){
 34     m=mt;
 35     n=nt;
 36     mn=m*n;
 37     matrixPtr=new double[mn];
 38 }
 39
 40 void Matrix::setMatrix(){
 41     cout<<"输入矩阵的行数和列数："<<endl;
 42     cin>>m>>n;
 43     mn=m*n;
 44     matrixPtr=new double[mn];
 45     for(int i=0;i<mn;i++)
 46         cin>>matrixPtr[i];
 47 }
 48
 49 void Matrix::transpose(){
 50     transposedMPtr=new double[mn];
 51     for(int i=0;i<n;i++)
 52         for(int j=0;j<m;j++)
 53             transposedMPtr[m*i+j]=matrixPtr[n*j+i];
 54 }
 55
 56 void Matrix::showMatrix(){
 57     for(int i=0;i<m;i++){
 58         for(int j=0;j<n;j++)
 59             cout<<matrixPtr[n*i+j]<<‘ ‘;
 60         cout<<endl;
 61     }
 62 }
 63
 64 void Matrix::showTransposedMatrix(){
 65     for(int i=0;i<n;i++){
 66         for(int j=0;j<m;j++)
 67             cout<<transposedMPtr[m*i+j]<<‘ ‘;
 68         cout<<endl;
 69     }
 70 }
 71
 72 Matrix operator *(Matrix m1,Matrix m2){
 73     Matrix m3(m1.m,m2.n);
 74     for(int i=0;i<m3.m;i++)
 75         for(int j=0;j<m3.n;j++){
 76             double val=0;
 77             for(int k=0;k<m2.m;k++)
 78                 val+=m1.matrixPtr[m1.n*i+k]*m2.matrixPtr[m2.n*k+j];
 79             m3.matrixPtr[m3.n*i+j]=val;
 80         }
 81     return m3;
 82 }
 83
 84 SquareMatrix::SquareMatrix(int m){
 85     Matrix(m,m);                      //right?
 86 }
 87
 88 void SquareMatrix::setSquareMatrix(){
 89     cout<<"输入方阵的阶数："<<endl;
 90     cin>>m;
 91     n=m;
 92     mn=m*n;
 93     matrixPtr=new double[mn];
 94     for(int i=0;i<mn;i++)
 95         cin>>matrixPtr[i];
 96 }
 97
 98 void SquareMatrix::setDet(){
 99     double valDet(double*,int);
100     det=valDet(matrixPtr,m);
101 }
102
103 void SquareMatrix::getDet(){
104     cout<<det<<endl;
105 }
106 double valDet( double *detPtr, int rank)
107 {
108     double val=0;
109     if(rank==1) return detPtr[0];
110     for(int i=0;i<rank;i++)                   //计算余子式保存在nextDetPtr[]中
111     {
112         double *nextDetPtr=new double[(rank-1)*(rank-1)];
113         for(int j=0;j<rank-1;j++)
114             for(int k=0;k<i;k++)
115                 nextDetPtr[j*(rank-1)+k]=detPtr[(j+1)*rank+k];
116         for(int j=0;j<rank-1;j++)
117             for(int k=i;k<rank-1;k++)
118                 nextDetPtr[j*(rank-1)+k]=detPtr[(j+1)*rank+k+1];
119         val+=detPtr[i]*valDet(nextDetPtr,rank-1)*pow(-1.0,i);
120     }
121     return val;
122 }
123
124 int main(){
125     Matrix m1,m2,m3;
126     m1.setMatrix();
127     m2.setMatrix();
128     m3=m1*m2;
129     m3.showMatrix();
130     return 0;
131 }